The image presents patterns of diffracted light that can result from scattering due to lightly falling rain. The picture shows two beams captured on a screen: the red laser beam is produced by a standard HeNe laser while the scattered green beam is produced by a laser-diode. The beams were expanded by using objective lenses of focal length equal to 50 centimetres. To simulate light rain, we used a simple alcohol-based cleaning spray to charge the air between the laser diode and the objective lens with falling liquid particles. In contrast, the red laser is not scattered by the spraying liquid particles and as such it can serve as a reference to the green light scattered by the liquid. We captured the patterns in the CIPHR lab University of Tartu Physicum building by using a phone camera and then we have digitally processed the image. The image was captured thanks to the efforst of three members of CIPHR and myself. First, we are very grateful to Professor Vijayakumar Anand, without whom this project would not exist. Professor Anand offered ideas and gently guided us at every turn. I would like to thank Professor Anand for his kind support and ongoing patience. Equally, I would also like to thank Dr. Praveen PA and Aravind Simon JR for their technical expertize, guidance and menthorship. Dr. Praveen PA helped align the lasers, and kindly processed the images. Aravind Simon JR had an equally valuable contribution by helping with alignment procedures and offering creative ideas to overcome technical difficulties. All members listed above, including myself, have contributed to this project.
—Andrei-Ioan Bleahu, University of Tartu, Tartu, Estonia
01 Dec 2022